Food products and other perishables are typically chilled either before, during or after processing to reduce bacterial growth and to retard onset of product spoilage. Ideally, food products such as seafood, meat and fish should be chilled to a temperature near but not at or below their freezing point to retain freshness. Such products must be shipped under chilled conditions in refrigerated or insulated containers containers in order to achieve sufficient shelf life and thus reduce waste during distribution.
Shipping cost is often the determinative factor in distribution to various markets of products tending to spoil rapidly if not shipped under chilled conditions which can be controlled within a relatively narrow temperature range. Refrigerated containers provide the desired temperature control but are usually heavy, bulky and expensive to operate. Moreover, since refrigerated shipping containers are usually transported by truck, rail or ship, these relatively slow modes of transportation serve to limit the area of distribution of such products. On the other hand, while insulated shipping containers are generally less bulky and thus more suitable for air transport than refrigerated containers, the insulated containers of the prior art have not provided the kind of temperature control necessary for shipping fresh seafood, meat and the like over extended periods of time. The end result has been either gradual rise to a undesireably high temperature or freezing of the fresh product within the container.
Although several insulated shipping containers have been developed heretofore, various difficulties have been associated with the apparatus and methods of the prior art. Difficulties with the prior insulated shipping containers have centered around their low product load/container weight ratios and inability to sustain chilled temperatures for sufficient duration. Moreover, the insulated shipping containers of the prior art have been relatively costly by reason of complicated construction, little or no reusability, and the requirement for special handling techniques and procedures when utilizing such containers. In general, the insulated shipping containers of the prior art have been too expensive and uneconomical for one time use. Return freight costs for nonreuseable containers can be substantial.
Various approaches have been taken to the problem of maintaining the proper product temperature within an insulated shipping container, including the use of dry ice or solid carbon dioxide as shown in U.S. Pat. Nos. 3,864,936, 2,236,052, 2,302,639, 2,915,235 and 1,998,681; however, the shipping containers and techniques of the prior art have been unsatisfactory for one reason or another.
A need has thus arisen for an improved process and container for shipping chilled perishables with greater efficiency.